Tuner



April 22, 1930. M. M. EELLS 1,755,982

TUNER Filed Sept. 20, 1926 2 Sheets-Sheet l Mi/Torz Merwr'rz [6/15 Patented Apr. 22, 1930 PATENT OFFICE MILTON MERWIN EELLS, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WILLIAM TURNOR LEWIS, OF RAC'INE, WISCONSIN TUNER Application filed September 20, 1926. Serial Ho. 136,626.

This invention relates to a tuning device adapted to be associated with a radio receiving set, so that the set may be more sharply tuned than under normal conditions.

Objects of this invention are to provide a device as an accessory and separate member from a radio set and adapted to be associated with the set so as to provide for sharper tuning than that intended for the set itself.

Further objects are to provide a tuning device which is compact, which is relatively cheap to construct, which is easy to handle, and which may be turned in any desired direction or moved towards or from the set to vary the coupling between the device and the set.

An embodiment of the invention is shown in the accompanying drawings in which:

Figure 1 is a sectional view transversely through the device Figure 2 is a sectional view on the line 22 of Figure 1;

Figure 3 is a diagrammatic view illustrating the association of the device with the set;

Figure 4 is a View of the inductance coil partly broken away as used in the device.

Referring first to Figures 1, 2, and 3, it will be seen that the auxiliary tuning device comprises a box-like casing 1, having a front panel 2 through which a tuning shaft 3 projects. *This tuning shaft 3 is operated by a knob 4L and carries a dial. 5. It operates the movable plates 6 of a condenser, indicated generally by the reference character 7, the stationary plates being indicated by the reference character 8. One terminal of this condenser, as indicated at 9, is connected by means of the conductor 10 to a binding post 11 (see Figure 3) on the rear side of the box or casing. The other terminal of the condenser as indicated by the reference character 12, is connected to an inductance coil 13 which may if desired, be of the spider web type. Preferably, this connection is effected through the medium of a rigid supporting arm 14% which terminates in an'eyelet 15 received under the nut of the terminal 12 of the condenser. This .rigid arm 14 is provided With a plurality of prongs, as indicated at 16, (see Figure 4) which are surrounded by insulating bushings 1' 7. These insulating bushings fit within the body of the coil 13, as most clearly shown in Figure 4. The other terminal 18 of the coil is connected to a binding post 19 (see Fig ure 3).

This tuning device also carries a phantom circuit consisting of a resistance 20 approximating the radiation resistance of the antenna with which the set is usually coupled, and a condenser 21 approximately of the capacity of such antenna. The terminals of this phantom circuit are connected to the binding posts 22 and 23, as shown in Figure 3.

In using the device, the binding posts 22 and 23 are connected to the input terminals or binding posts 24 of the receiving set, such set being usually positioned within a housing or box, as indicated at 25. The tuner is placed adjacent the first inductance coil 26 of. the receiving set, such coil being normally connected to a tuning condenser 27.

The binding posts 11 and 19 are connected to the ground 28 and to the antenna 29, as indicated in Figure 3.

The coils 13 and 26 are thus electromagnetically coupled so that the device will energize the receiving set although the receiving set is disconnected from the antenna and ground. The radiation resistance and the capacity of the antenna are replaced by the resistance'20 and condenser 21 of the phantom circuit, so as not to upset the constants or characteritsics of the receiving set.

Obviously, the tuner may be movedtowards or from the receiving set to vary the inductive coupling existing between the coils 13 and 26. Obviously, the tuner may be turned so as to cause parallelism between the axis of the'coils 13 and 26 however the coil 26 is arranged in the receiving set, and it should be positioned in proximity to this first inductance coil of the receiving set. In using the device, the tuning of the radio receivingset is, effected in the usual manner and the tuning of the auxiliary device or tuner is a.-

secured by varying the capacity of the condenser. Olearly, other tuning devices could be used.

It will be seen, therefore, that a novel form of auxiliary tuner has been provided for radio receiving sets so that the constants and 'pling of said set to the antenna may be varied.

characteristics of the set are not disturbed and yet a very much sharper tuning results.

It Will be seen further that the tuner is very simply constructed and may be cheaply manufactured.

1 Although the invention has been described in considerable detail, such description is intended as illustrative rather than limiting as the'invention may be variously embodied and as the scope of such invention is to'be deter"- mined as claimed.

I claim 1. A tuner for radio. receiving sets com-- prising a variable condenser and an inductance COll connected together and to input terminals, a phantom'circuit having a con minals, a box housing said condensers, coil,

being a rigid support therefor and being rigidly connected to the terminal of the variable condenser. I

.2. The combination of a radio receiving set having a coil and a tuning condenser'electr1cally connected and having lllllllIlELlS. connectedto said condenserand coil and adapted for connection to an antenna and a ground connection, an auxiliary member consisting of a bodily movable cabinet having a pair of terminals, said pair or terminals being elec-' trically connected to said first mentioned terminals, a phantom circuit including a condenser and a resistance carried Within said cabinet and connected to said second mentioned terminals, a coil and a variable condenser carried Within said cabinet and connected to asecond pair of terminals carried by said cabinet, saidlast pair ofterminals bemg adapted for connection to the antenna and the ground connections, whereby said in said cabinet securing independent tuning of the antenna circuit.

7 3. A device adapted to be connected to a radio receiving set. having input terminals and having a coil, and adapted to be con.-

'nected to an antenna and'a ground, said:-de-

vice comprising a cabinet, a circuit including a. resistance and a condenser located in said.

cabinet, terminals connected to said circuit In testimony that I claim the foregoing I have hereunto set my hand at Racine, in the county of Racine and State of Wisconsin.

MILTON MERWIN EELLS.

' denser and a resistance and connected to ter and adapted to be connected to said receiving Y set, and an oscillation circuit including a coil adapted to be connected to the antenna and tothe ground, said coil being adapted to be inductively related to the receiving set, and 7 said first mentioned circuit being adapted to I v be directly connected to the terminals of said receiving set, whereby the loading of said set may be kept constant and the inductive cou 

